1. Field of the Invention
The present invention relates to an automated apparatus for extracting liquid samples, particularly biological fluids such as urine, blood serum, plasma, cerebrospinal fluid and the like, from a container. In particular, the present invention provides an improved method to automatically extract a desired amount of liquid sample from a closed container in preparation for clinical diagnosis.
2. Description of the Related Art
Clinical laboratories are routinely required to remove all or a portion of liquid samples from collection containers and a number of automated sampling systems have been produced to assist this operation. Generally, these systems receive sample containers, remove a predetermined quantity of sample from each container at a first location, and transfer the removed sample to a second location for analysis. The sample containers usually used with these systems are open-top vials or tubes transported in the system on carousels, racks or linear transports and then transferred between such devices with mechanical pusharms or other similar mechanisms.
Using open sample containers in an automatic sampling system presents a number of problems. First, the various forces which move the containers through the system cause spills and contamination. Second, open sample containers expose an operator to any harmful substances disposed in the containers. Finally, because open containers require special care, the cost of operation increases.
To avoid these problems, samples to be tested in automated clinical analysis systems are often collected in evacuated glass tubes closed with rubber stoppers and sealed with a vacuum. The sample displaces part of the vacuum; but some vacuum may remain. Removal of the stopper may result in the formation of aerosol particles. Consequently, when an operator removes the stopper before placing the container in the automated system, the aerosol spray may expose the operator to any harmful substances contained in the sample. In addition, removal of the stopper manually by the operator increases the cost of operation and decreases the efficiency and reliability of an automated system.
One solution to these problems is to present a closed container containing the sample to be analyzed to the automated analysis system and to employ an automated sampling system adapted to extract a known amount of liquid sample through the stopper of a closed tube or vial. To do so, available sampling system include an arrangement of needles, purge mechanisms, gas pressurization and other complex techniques to take samples from sealed sample containers. In addition to requirements placed on these sampling systems to remove at least a predetermined amount of liquid, concerns remain over the quality of the extracted sample, so that it be free of disruptive nonhomogenities like clots or bubbles.
U.S. Pat. No. 4,794,085 describes an apparatus and a method which permit the detection of penetration of liquid by an apertured container used for aspirating and dispensing the liquid. The apparatus has control means for advancing the container an increment of the maximum possible distance to the liquid, means to generate a pressure differential within the dispensing container that is sufficient to generate a signal that is indicative of whether the container aperture is closed by the liquid, and devices to detect and signal the pressure produced within the container by such a pressure differential, and to compare the signaled pressure against a reference
U.S. Pat. No. 4,926,701 describes a pipetting device comprising a probe for dipping into a reservoir, reaction vessel or the like, a metering pump connected to the probe and a shutoff valve disposed between the probe and the pump are provided. In the intake phase of the pump with the valve open, first air and then a predetermined quantity of liquid is taken in. For at least some of the delivery phase of the pump the valve is in the closed state so that a pressure builds up in the pump. At the end of the delivery phase the valve opens whereby due to the high pressure any adhering liquid particles are expelled.
U.S. Pat. No. 4,951,512 provides for providing access to a sealed container which temporarily provides an opening in the closures of the containers, and either removes contents, senses properties of the contents, or dispenses material into the container. A lift assembly moves each sample container upward against a puncture tube to produce an opening in the closure of the container. The system takes a sample through this opening or inserts a probe through the opening to measure the properties of the sample.
U.S. Pat. No. 5,163,582 covers an apparatus and method for dispensing a predetermined volume of liquid from a closed, liquid-containing blood collection tube is described. The apparatus includes a dual conduit providing a passageway for liquid to be dispensed from a closed blood collection tube and a gas conduit providing a passageway for gas to be introduced into the blood collection tube. Included in the apparatus is insertion of the dual conduit into the blood collection tube, turning the tube away from a vertical, upright orientation, connecting and disconnecting the gas passageway from a gas supply, displacing a volume of gas through the gas passageway, and controlling the operation of the apparatus. A method is also disclosed involving insertion of a dual conduit into a closed blood collection tube, connecting a gas supply to a gas conduit of the dual conduit, rotating the tube away from a vertical, upright orientation, introducing a volume of gas corresponding to a signal into the blood collection tube, receiving a predetermined volume of liquid from the blood collection tube, and physically disconnecting the gas supply from the gas passageway.
U.S. Pat. No. 5,413,246 discloses a disposable apparatus to dispense an amount of liquid from a closed container using a stopper piercing means to access the interior of a closed blood collection tube, a gas passage means to allow a metered amount of gas to be forced into the blood collection tube, and a liquid passage means to allow fluid to be dispensed from the tube in proportion to the amount of gas forced into the tube. Also disclosed is a machine which uses a disposable apparatus to dispense liquid from a sequence of closed blood collection tubes in an automated manner. Liquid contained within a blood collection tube is dispensed from the tube by a control means according to signals indicative of the amount of liquid within the tube and the amount of liquid that is desired to be dispensed. A manually operated machine that uses the disposable apparatus to dispense a sample of liquid from a closed blood collection tube is also described.
U.S. Pat. No. 5,499,545 is a method for improving measurement accuracy by eliminating the influence of changes in the atmospheric and internal pressures on the quantity of a liquid absorbed or discharged. A pipetting device inducts a specified quantity of liquid into a tip portion or discharges a specified quantity of liquid from the tip portion by controlling the pressure inside a cylinder portion including a cylinder and a piston. A control target value for the quantity of the liquid to be absorbed or discharged from a command portion and information from an atmospheric pressure measurement portion and a pressure sensor for detecting the internal pressure of the cylinder are sent to a correction calculation portion which in turn performs correction calculation based on measured data on the atmospheric and internal pressures and data on the shapes of the cylinder and tip portion to obtain the distance to be traveled by the piston so that the control target value form the command portion is met. A control portion controls a motor which drives the piston in accordance with information on the distance to be traveled by the piston from the correction calculation portion.
Accordingly, from a study of the different approaches taken in the prior art to the problems presented by the necessity for efficiently extracting a known amount of liquid from a closed container, taken with the challenge of ensuring that the extracted sample be free of disruptive nonhomogenities, there remains a need for an improved approach to provide liquid samples to an automated clinical analyzer without introducing complex control mechanisms and without unduly adding to the resources required.